Browsing behaviour in complex ungulate multi-species systems in Southern Sweden

Abstract: In recent years several of the ungulate species present in Sweden have increased in both densities and distribution. Browsing pressure has mainly been attributed to moose but recent research shows that with more complex ungulate ecosystems new interactions and connections might emerge. This thesis serves to investigate the im-pact of multi-species ungulate communities on browsing pressure in boreal forests and semi-open landscapes in southern Sweden. In this study the effect of ungulate species densities, richness and feeding strategy on browsing pressure were analyzed. This study uses data collected within the ongoing environmental analysis project “ref-erence areas for management of ungulates in southern Sweden”. Total weighted browsing pressure, tree species specific browsing pressure and ungulate densities were monitored. The data was analyzed using generalized linear mixed models. Final model selection was done using Akaike information criterion (AIC). In order to in-clude different ungulate species in the same models ungulate densities were trans-formed into moose equivalents. GLMM models showed that ungulate species rich-ness, ungulate density and ungulate feeding strategy all have a significant effect on browsing pressure. Ungulate species richness had a negative impact on browsing pressure which likely means that increased interspecific competition could cause a decrease in browsing pressure. Ungulate total density had a positive effect on brows-ing pressure, which was not unexpected given previous research on the subject. Feed-ing strategy was found to have some, although weak indications that it could be a contributing factor to browsing pressure. In all the final models moose had a rela-tively large positive estimate, which agree with previous studies that moose is one of the main perpetrators behind browsing pressure carried out by ungulates in Sweden. To conclude there are clear indications that new interactions and connections will emerge with changing ungulate populations.